The present invention relates in general to balancing and specifically to determining the magnitude and the phase position of oscillations detected by means of pickups. A useful signal, which is essentially composed of an amplitude and a frequency, is filtered out of the measured signal by frequency selection. The inventive method and apparatus are especially employed in techniques for the measurement of unbalances in rotors.
In rotor balance measuring techniques it is well known to filter the measured signal composed of an amplitude A.sub.n and a frequency sin (n.omega.t), with n.omega. being the rotor frequency, out of a mixture of oscillations by means of various different selecting procedures. These selecting procedures include, for example, Fourier analysis, the wattmeter, Hall generators, phase-sensitive rectification, or even simple RC-filters.
All these procedures, however, do not permit obtaining the theoretically ideal selection, since unavoidable errors will occur. External oscillations are the source of most of the errors, which adversely influence the test result.
From an economic point of view, most of the time it cannot be justified to minimize or eliminate these small errors, which are classified as signal frequency errors.
Furthermore, these are also amplitude errors, which have been minimized up to now in the well-known measuring techniques simply by raising or tightening the tolerance limits.
Such errors, for example, comprise: crosstalk errors in plane separation; changes of sensitivity; centering errors of the machine; errors in the radii or the planes; as well as errors in the electronic measuring system.
Reduction of the class of frequency errors, by means of perfect filtering procedures, is as necessary and important as the tightening of the manufacturing tolerances; in both cases, however, an economically justifiable degree of accuracy should be achieved. Therefore, it is an object of the present invention to provide for optimum exploitation of information, during a data determination procedure of the above-mentioned kind, by making use of mathematical procedures which permit determination of the magnitude and the phase position of vibratory oscillations detected by pickups in a rotor-balancing operation.